Device for controlling coolant pressure in evaporator

ABSTRACT

A mechanism for regulating pressure in an evaporator is provided integrally with a collecting chamber for collecting a coolant from an evaporator, which chamber is provided in a valve for controlling an expansion rate of a coolant, said valve being disposed in a heat cycle system for use in a car cooler or the like, thereby presenting ease in installation, ease in maintenance and ease in manufacture.

IJnited States Patent Takahaslii et a1.

1 Dec. 24, 1974 FROM EVAPORATOR DEVICE FOR CONTROLLING COOLANT PRESSUREIN EVAPORATOR Inventors: Reijiro Takahashi; Kazuo Kanemoto, both ofKatsuta; Toshikatu Ito, lbaraki-ken, all of Japan Assignee: Hitachi,Ltd., Tokyo, Japan Filed: Jan. 23, 1974 Appl. No.: 435,971

Foreign Application Priority Data Jan. 24, 1973 Japan 48-9542 US. Cl.62/217, 62/225 Int. Cl. F251) 41/04 Field of Search ..-62/204, 210, 209,222-225,

References Cited UNITED STATES PATENTS Carter 62/225 2,463,951 3/1949Carter 62/225 2,642,724 6/1953 Carter A 62/225 3,640,036 2/1972 Brody62/210 3,785,554 1/1974 Proctor 62/224 Primary Examiner-Meyer PerlinAttorney, Agent, or FirmCraig & Antonelli [57] ABSTRACT A mechanism forregulating pressure in an evaporator is provided integrally with acollecting chamber for collecting a coolant from an evaporator, whichchamber is provided in a valve for controlling an expansion rate of acoolant, said valve being disposed in a heat cycle system for use in acar cooler or the like, thereby presenting ease in installation, ease inmaintenance and ease in manufacture.

8 Claims, 6 Drawing Figures FROM LIQUID RECEIVER 'TO EVAPORATOL l T oCOMPRESSOR PATENTEU '9 5.855.836

sIIEI1I =3 FROM LIQUID RECEIVER E To EVAPORATOL] IO H FROM EVAPORATOR: IH 2O I sv I {lo COMPRESSOR ,L--- I5 I I l9 6 mmgnnsczmm 3,855,836

sum-2953 FlG.3

FROM LIQUID RECEIVER 7 1 TO EVAPORATO I III a1? FROM EVAPORATOR PATENTEUUEC24|974 SHEU 3 OF 3 EXPANSION VALVE OPERABLE RANGE HEAT LOAD ONEVAPORATOR m mmnmwwmm i P A a FIG.6

FROM EVAPORATOR BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to a coolant controlling device for use in an airconditioning apparatus, and more particularly to a mechanism forcontrolling a coolant pressure in an evaporator.

2. Description of the Prior Arts It is a recent trend to use anair-conditioning unit through all seasons. In case a cooling cycle isused in a wide range of ambient temperatures, especially in a lowtemperature zone, there is experienced growth of frost or the freezingof moisture on an evaporator. Usually, the evaporator is so designed asto fulfil the satisfactory cooling performance, even when a high levelof heat load is applied thereto. Accordingly, in case the heat loadbecomes lower, for example, in case the ambient temperature becomeslower and only the dehumidification is desired, the coolant evaporatingpressure in the evaporator becomes lowered beyond the coolantcontrolling capability of the expansion valve. This brings about aphenomenon of the frozen outer surface of the evaporator, i.e., thegrowth of frost or a phenomenon that the coolant remains in the liquidstate, thus incurring a risk of breaking various units of system, forexample, a compressor of being broken. To avoid such a problem, it isrequired that the minimum evaporating pressure in the evaporator be setto a level at which no growth of frost arises, so as to causeevaporation of the coolant usually at a pressure over the predeterminedlevel. Hitherto, to prevent the freezing of an evaporator or the like,the coolant evaporating pressure controlling device has been used. Sucha coolant evaporating pressure controlling device, because it isindependent of the other units of cooling system, presents variousproblems and difficulties in that there have to be provided variouspipings for connecting the units, such as heat sensitive pipes,pressure-equalizing pipes or the like, resulting in the complicateconstruction, the leakage of gas, lowering of the efficiency ininstallation, and increase in the manufacturing cost as well as in aspace required for the unit.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a device for controlling a coolant pressure in an evaporatorwhich is superior in ready maintainance and good accessibility.

Another object of the present invention is to provide a device forcontrolling a coolant pressure in the evaporator which is simple andeasy in the maintenance and check.

A further object of the present invention is to provide a device forcontrolling a coolant pressure in an evaporator which is small in sizeand superior in the controlling capability.

The present invention is directed to providing a pressure controllingvalve mechanically integral with a collecting chamber leading to anoutlet port of an evaporator, said collector serving to collect thecoolant from the evaporator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a cooling systemrelating to the present invention;

FIG. 2 is a longitudinal cross-sectional view illustrating an expansionvalve and a pressure control valve of FIG. 1.

FIG. 3 is a modification of FIG. 2.

FIG. 4 is-a plot representing heat load exerted on an evaporator and acharacteristic of a diaphragm responsive to temperature and pressure ofa coolant within the evaporator.

FIG. 5 is an enlarged view of a spindle of FIGS. 2 and 3, and

FIG. 6 is a further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The description will be givento preferred embodiments of the present invention in conjunction withthe accompanying drawings.

Referring to FIG. 1 which shows an embodiment of a cooling systemaccording to the present invention,

shown at 1 is a compressor for compressing a coolant into a gaseouscoolant of high temperature and high pressure, at 2 is a condenser forcooling the gaseous coolant for liquidification, at 3 is a liquidreceiver, in which the coolant is separated into gas and liquid, and at4 is an expansion valve control portion in which the liquid coolant fromthe liquid receiver 3 is subjected to expansion to be fed to anevaporator 6. The coolant gas from the evaporator 6 returns via apressure control valve portion 14 to the compressor 1 to control thepressure in the evaporator 6.

The expansion valve control portion 4 and the pressure control valveportion 14 are illustrated in detail in FIG. 2. Referring to thedrawing, the expansion valve control portion 4 includes a distributor 7for introducing the coolant from the expansion valve 5 into theevaporator 6, and a collector 8 for recovering same, said distributor 7and collector 8 being constructed integrally with each other. Thecollector 8 is partitioned by an expansion-valve actuating diaphragm 12into a primary chamber 9 (a heat sensitive chamber) and a secondarychamber 10, both of which are communicated with each other by way of aconnecting pipe 11 provided in a body proper of the device. Theaforesaid expansion-valve actuating diaphragm is provided therein with aheat sensitive member 20 which is sealingly filled therein, with itssecondary chamber side being communicated by way of a connecting rod 13with a valve body, such as a ball valve of the expansion valve 5. Theexpansion valve 5 is so adapted as to control a flow rate of coolantfrom the liquid receiver 3 and to be closed by means of a spring or thelike when the pressure in the primary chamber 9 becomes low.

The pressure control valve portion 14 includes a valve body 19 and aspindle 15, a bellows 16, a spring 17 and an adjusting screw 18.

Referring to the relationship of the pressure set by the adjustingmeans, which includes the aforesaid spring 17 and adjusting screw 18, tothe pressure in the primary chamber 9, if the pressure in the primarychamber 9 relatively increases, the spindle 15 is forced downwardly,thereby bringing an outlet port 21 of pres sure control valve portion 14into communication with the primary chamber 9. Accordingly, the pressurein the evaporator 6 may be maintained at a level above the pressurewhich has been set by said adjusting means.

With the provisions described, the coolant gas of high pressure and hightemperature from the compressor 1 is cooled in the condenser 2 to aliquid state then introduced into the liquid receiver 3, followed by theabrupt pressure-reduction in the expansion valve 5, then heatexchangedin the evaporator 6, and then returned by way of the pressure controlvalve portion 14 into the compressor 1. However, with the drop in theambient temperature, the coolant evaporating pressure in the evaporator6 will be decreased to a large extent resulting in the breakage of thecooling system due to freezing or the like. To avoid this drawback, thecoolant, in the embodiment described, is introduced from the liquidreceiver 3 into the expansion valve control portion 4 as well as thepressure control valve portion 14 which are provided integrally witheach other. In detail, the expansion valve 5 in the expansion valvecontrol portion 4 is so designed as to open or close its valve body,such as a ball, by means of the connecting rod 13, depending upon thepressure difference between the internal pressure which varies accordingto the change in temperature of heat sensitive member 20 sealinglyfilled in the diaphragm 12, which change is caused due to the coolantintroduced in the collector 8 from the evaporator 6, and the pressure inthe secondary chamber 10 of the collector 8 which is communicated by wayof the communicating passage 11 with the primary chamber 9 thereof.Thus, the coolant may be introduced in a proper amount accordingly, sothat the breakage in the cooling system or reduction in the performancethereof due to freezing may be avoided, with the result of the stableperformance. Furthennore, the coolant collector 8 and the pressurecontrol valve portion 14 are provided integrally with each other, withthe pressure of the coolant in the collector 8 being exerted on the sideof spindle 15 of the bellows 16, so that the movement of the spindle 15may be controlled by ballancing the pressure in the collector 8 and thespring force of spring 17, thereby controlling the flow rate of coolant,thus controlling the internal pressure in the evaporator 6. It isnatural that the critical pressure may be set up by exerting the springpressure on the bellows 16 by turning the adjusting screw 18. Now,suppose that a letter A represents the effective area of bellows 16, Kthe spring constant of spring 17, P the gas pressure sealingly filled inthe heat sensitive chamber 20 of the expansion valve portion 4, F thespring pressure at the time of set up, and AL the torsion of the springduring its operation (the movement of the spindle), then an equation P XA F K X AL will be obtained, in which the critical pressure is obtainedas AL 0, and then P WA. This pressure can be utilized as the value foravoiding the frosting. Thus, the heater portion of the evaporator 6 isused as a part of the expansion valve portion 4 and pressure controlvalve portion 14, so that the construction of the control system may berendered simple and compact. In this case, if the pressure control valveportion 14 may be integrally formed under the collector 8, consideringthe fluidity of the internal liquid within the expansion valve controlportion 4 and pressure control valve portion 14, then the circulation ofthe coolant to the compressor will be facilitated, without causing atrouble in the compressor due to oil shortage. In addition, this bringsabout another advantage that no oil return passage is required, althoughsuch a passage is essential where the expansion valve control portion 4and the constant pressure control valve portion 14 are separatelyprovided, and that no oil sump is required in the piping.

FIG. 3 shows a modification of the device of FIG. 2. This isdiscriminative from FIG. 2 in that a communicating passage 11 isprovided in the body proper 19 of the device, which comprises theexpansion valve control mechanism and pressure control valve mechanism,in a manner to communicate the secondary chamber 10 of collector 8 withthe outlet port 2] of pressure control valve, and the actuation of theexpansion valve 5 is effected by a pressure difference caused betweenthe aforesaid output port 21 of pressure control valve (the pressure inthe secondary chamber 10) and the diaphragm portion. This is mostadvantageous where the characteristics in the heat sensitive members ofdiaphragm and that of the secondary pressure portion do not present theequlibrium in temperature and pressure such as shown in FIG. 4. In FIG.4, Fe is representative of the secondary pressure in the diaphragm, Pt aheat sensitive pressure in the diaphragm, Q a heat load in theevaporator 6, and AP a critical pressure difference, and if the pressuredifference becomes larger than the critical pressure difference, thenthe expansion valve 5 is brought into its fully open position. In thedevice of FIG. 2, it is required that the valve rod of expansion valve 5be forced downwardly so as to keep opening the orifice by overcoming theevaporating pressure, i.e., the critical pressure, or the pressurecontrol valve pressure. On the other hand, in the device of FIG. 3,since the pressure lower than the pressure of the low pressure controlvalve acts on the diaphragm, the relationship as plotted in FIG. 4 isnot required in a strict sense. Accordingly, if the controlling valveactuating range is set to a point just above the critical freezingpoint, no accurate control means is required, and thus the readymanufacture of the control valve will result.

In FIG. 4, represented by Fe is the secondary pressure of the coolant,which is the pressure in the secondary chamber 10 of FIGS. 2 and 3.Represented by Pt is the pressure corresponding to the change in thecoolant temperature in the primary chamber 9 or the collector 8. As thepressure in the evaporator decreases, the pressure in the secondarychamber 10 decreases, thereby opening the expansion valve. With thetemperature drop, the expansion valve will be closed. The aforesaidpressure P6 and Pt act on the expansion valve in a manner that thepressure Pt acts to open the valve and the pressure Pe acts to close thevalve. Accordingly, the pressure difference AP between Pt and Fe may bereferred to as an open angle of the expansion valve. When the heat loadis decreased to less than O1, in other words, when ambient temperatureis dropped, the pressure control valve will be brought into actuation.By the action of the pressure control valve, the pressure Pe remains ata given pressure level. Depending upon the operational conditions, thepressures Pt and Pe will have a close access to each other. At thistime, hunting may occure, with the accompanying vibration of theconstant pressure controlling valve. To avoid such a phenomenon, thedifference between Pt and Fe should be large. It is preferable from thisviewpoint that the outlet port 21 of pressure control valve becommunicated with the secondary chamber as shown in FIG. 3.

FIG. 5 is an enlarged view of the spindle of FIGS. 2 and 3. The spindle15 has a cylindrical bore provided centrally thereof and communicatingby way of orifices 31 with space 33. The pressure of coolant istransmitted through said orifices, via the outside of a flange 35serving as a resistor, and via the outside of a stopper 37 or through acut-away portion 39, and eventually to the bellows 16. The reason whythe pressure of the coolant introduced in the collector 8 from theevaporator is applied via the resistor means to the bellows 16 is thatthe bellows 16 may be controlled for its responsiveness, and thevibration of the spindle 15 may be prevented.

FIG. 6 illustrates a further embodiment of the present invention. Inthis embodiment, the expansion valve control portion is providedindependently, likewise in the conventional device, while the collector8 for collecting the coolant from the evaporator and the pres surecontrol valve portion 14 are formed integrally with each other. Such aconstruction is also advantageous from the viewpoint of performance. Theefficacy of the device will be greatly increased by providing theexpansion valve integrally with the pressure control valve portion, asshown in FIGS. 2 or 3. In FIG. 6, the distributors for supplying thecoolant to the expansion valve and the evaporator are separatelyprovided one from another. The spindle 15 is the same in construction asthat of FIG. 5.

Although the expansion valve and the pressure control valve in FIGS. 2and 3 are formed integrally, it is recommendable that the manufactureand the testing be individually carried out, after which those membersbe assembled together, with mechanical sealing rings being interposedtherebetween for preventing the leakage of the coolant therefrom.

What is claimed is:

l. A pressure control valve for:

a cooling system having,

a compressor for compressing a coolant,

a condenser for condensing the coolant compressed in said compressorinto a liquid,

a liquid receiver for separating the coolant from the condenser intoliquid and gas,

an expansion valve for subjecting the liquid coolant from the liquidreceiver to expansion,

an evaporator for causing heat-exchange between coolant gas from theexpansion valve and air,

a pressure control valve for maintaining the pressure in the evaporatorat a level higher than a predetermined level, and

means for returning the coolant gas from said pressure control valve tothe compressor; characterized by that said evaporator includes aplurality of coolant gas passages arranged in parallel and a collectorfor collecting the coolant flowing through said plurality of the coolantgas passages;

a housing mechanically connected with said collector;

a biasing means provided in said housing, said biasing means having oneside, to which is exerted the gas pressure in the collector;

a spring for exerting a force on the other side of said biasing means;

an adjusting screw for adjusting the pressure of the spring; and

a valve means provided between the collector and the means for returningthe coolant to the compressor and having an opening capable for varyingits size.

2. A pressure control valve as defined in claim 1, wherein said valvemeans has a substantially cylindrical bore communicating with saidcollector, and a substantially cylindrical movable means retained withinsaid cylindrical bore and adapted to be moved by said biasing means;

said substantially cylindrical bore communicating with said collectorand having a diametrically enlarged space at a predetermined distanceapart from said collector;

an exit port provided through said housing so as to communicate to saiddiametrically enlarged portion for discharging the coolant gas;

said movable means actuated by said biasing means being provided with anotched portion near to the collector;

whereby said ports is brought into communication by way of said notchedportions when said movable means is urged under the pressure in thecollector towards said spring.

3. A pressure control valve as defined in claim 2, wherein said biasingmeans being adapted to air-tightly seal a portion between saidsubstantially cylindrical movable means and said spring so as not tocause a leakage of gas, and said movable means is provided with acylindrical inner bore, through which the gas pressure in said collectoris exerted on the side of movable means of said biasing means.

4. A pressure control valve as defined in claim 3, wherein said springurging at its one end thereof said biasing means to the side ofcollector and being retained at the other end by the adjusting screwprovided in the housing, said spring being changable in length due torotation of said adjusting screw.

5. A pressure controlling valve as defined in claim 4, wherein adiaphragm is provided in said collector chamber, said diaphragm havingone surface, to which is applied the pressure in the collector chamberand the other surface, to which is applied the pressure in the collectorby way of a passage having a large resistance, said diaphragm holdingthe gas or liquid expansible with the temperature rise, and controllingthe expansion valve by biasing the other surface of the diaphragm.

6. A pressure control valve as defined in claim 5, wherein said biasingmeans includes a bellows, and a passage communicating said bellows withsaid collector having a cylindrical central bore provided in the centerof said movable means and, a resistive passage crossing said movablemeans and formed between said movable means and an inner wall of saidcylindrical bore of said housing which is adjacent to the bellows.

7. A pressure control valve as defined in claim 4, wherein one side ofsaid diaphragm constituting a wall of the collecting chamber and theother side thereof constituting a wall of other space, and other spacebeing communicated by way of passages with an outlet port of saidpressure control valve.

8. A pressure control valve as defined in claim 6, wherein said biasingmeans consists of a bellows, and a passage communicating the bellowswith the collecting chamber having a cylindrical central bore providedin the movable means, and a resistive passage crossing said movablemeans and formed between said movable means and an inner wall of saidcylindrical bore of said housing which is adjacent to the bellows.

1. A pressure control valve for: a cooling system having, a compressorfor compressing a coolant, a condenser for condensing the coolantcompressed in said compressor into a liquid, a liquid receiver forseparating the coolant from the condenser into liquid and gas, anexpansion valve for subjecting the liquid coolant from the liquidreceiver to expansion, an evaporator for causing heat-exchange betweencoolant gas from the expansion valve and air, a pressure control valvefor maintaining the pressure in the evaporator at a level higher than apredetermined level, and means for returning the coolant gas from saidpressure control valve to the compressor; characterized by that saidevaporator includes a plurality of coolant gas passages arranged inparallel and a collector for collecting the coolant flowing through saidplurality of the coolant gas passages; a housing mechanically connectedwith said collector; a biasing means provided in said housing, saidbiasing means having one side, to which is exerted the gas pressure inthe collector; a spring for exerting a force on the other side of saidbiasing means; an adjusting screw for adjusting the pressure of thespring; and a valve means provided between the collector and the meansfor returning the coolant to the compressor and having an openingcapable for varying its size.
 2. A pressure control valve as defined inclaim 1, wherein said valve means has a substantially cylindrical borecommunicating with said collector, and a substantially cylindricalmovable means retained within said cylindrical bore and adapted to bemoved by said biasing means; said substantially cylindrical borecommunicating with said collector and having a diametrically enlargedspace at a predetermined distance apart from said collector; an exitport provided through said housing so as to communicate to saiddiametrically enlarged portion for discharging the coolant gas; saidmovable means actuated by said biasing means being provided with anotched portion near to the collector; whereby said ports is broughtinto communication by way of said notched portions when said movablemeans is urged under the pressure in the collector towards said spring.3. A pressure control valve as defined in claim 2, wherein said biasingmeans being adapted to air-tightly seal a portion between saidsubstantially cylindrical movable means and said spring so as not tocause a leakage of gas, and said movable means is provided with acylindrical inner bore, through which the gas pressure in said collectoris exerted on the side of movable means of said biasing means.
 4. Apressure control valve as defined in claim 3, wherein said spring urgingat its one end thereof said biasing means to the side of collector andbeing retained at the other end by the adjusting screw provided in thehousing, said spring being changable in length due to rotation of saidadjusting screw.
 5. A pressure controlling valve as defined in claim 4,wherein a diaphragm is provided in said collector chamber, saiddiaphragm having one surface, to which is applied the pressure in thecollector chamber and the other surface, to which is applied thepressure in the collector by way of a passage having a large resistance,said diaphragm holding the gas or liquid expansible with the temperaturerise, and controlling the expansion valve by biasing the other surfaceof the diaphragm.
 6. A pressure control valve as defined in claim 5,wherein said biasing means indudes a bellows, and a passagecommunicating said bellows with said collector having a cylindricalcentral bore provided in the center of said movable means and, aresistive pAssage crossing said movable means and formed between saidmovable means and an inner wall of said cylindrical bore of said housingwhich is adjacent to the bellows.
 7. A pressure control valve as definedin claim 4, wherein one side of said diaphragm constituting a wall ofthe collecting chamber and the other side thereof constituting a wall ofother space, and other space being communicated by way of passages withan outlet port of said pressure control valve.
 8. A pressure controlvalve as defined in claim 6, wherein said biasing means consists of abellows, and a passage communicating the bellows with the collectingchamber having a cylindrical central bore provided in the movable means,and a resistive passage crossing said movable means and formed betweensaid movable means and an inner wall of said cylindrical bore of saidhousing which is adjacent to the bellows.